Trimble GCS900 Grade Control Systems are running on a dozer, compactor, and motor grader. The heavy equipment is equipped with dual-mast Trimble MS990 or MS992 Smart GPS Antennas.
Delta Construction used Trimble's SPS930 Universal Total Station to guide the machines to achieve the fine grade they want.
Delta Construction, Oahu, Hawaii, is in the final stages of a $20 million, 60-acre residential housing site prep project for the Department of Hawaiian Home Lands (DHHL). As part of an affordable housing program, DHHL will offer residential home sites to qualified individuals who are more than 50% native Hawaiian. The house site is free, so all they pay for is the cost of the home construction.
"Because land is limited, typical house costs range from $400,000 to $800,000, so DHHL is helping local people enter into home ownership at about half the cost," notes J.R. Chambliss, GPS survey manager for Delta Construction.
DHHL functions as the project management company, controlling the costs on the East Kapolei Two project, which includes 1,200 home sites, as well as a youth center, community hall and swimming pool. TThe site also calls for excavating and sub-grade for a 100-foot wide, mile-long dramatic parkway entrance into the subdivision. There is a shoulder and 8-foot sidewalks on both sides, with tree planter areas dividing the two lanes running in each direction.
Controlling costs with GPS
Delta management recognized it could benefit from the use of technology on the project. Because of the site's size, a large amount of fill will be imported to the island.
"We have about 166,000 yards of cut-to-fill on the site, and about 150,000 yards of select fill, which is coral," Chambliss says. "The reason we use coral is because it's non-expansive material. It works like select fill or good gravel that you would use on the mainland.
"Over-running the imported fill material by an inch or two throughout the 60-acre site would cause us to exceed our budget by 10% or more," he continues. "That's why using Trimble systems on this project was essential. Otherwise, we could see higher costs for trucking, fuel, personnel, and on and on."
Trimble GCS900 grade control systems are in use on a dozer, compactor and motor grader. The heavy equipment is equipped with dual-mast MS990 or MS992 Smart GPS Antennas. The SPS930 Universal Total Station (UTS) is used to guide the machines to achieve fine grade. The UTS is also used for survey, layout and topos.
Delta constructs its own 3D digital site plans. "We built both the subgrade and finish grade models," states Chambliss. "Traditionally, our survey budget would be substantial since we would have surveyors out there pretty much full time. When we're running that many scrapers, dozers and compactors, they'll be knocking down stakes left and right and the surveyors would need to re-set them. "
Chambliss estimates that using machine control and a 3D model has saved the company significantly in surveying costs on this project.
Convincing the site superintendent
Despite the potential benefits of GPS grade control, not everyone was onboard with the process at the outset.
"A challenge on the project was getting the site superintendent comfortable with the GPS technology," Chambliss comments. "He was very nervous about not seeing stakes with ribbons on them throughout the site. To make him feel comfortable and in control, I equipped a Gator 4X4 with a rover — a Trimble SPS882 Smart GPS Antenna — so that he had access to all the site and workflow data the machine operators have in their cabs."
Having access to the information allowed the site superintendent to think strategically about the project. "When material is delivered or dirt needs to be stockpiled, superintendents typically would say, 'just put it over there,'" Chambliss says. "But with the rover, the super can look and say 'don't put it there, because we'll be working there next.'
"I spent a lot of time showing him and teaching him how the technology works, how best to use it, and how to best take advantage of it," he adds. "He turned the corner and began to see how immensely powerful and helpful the systems are. He now understands that GPS or ATS on machines are tools... incredibly beneficial tools. Now he's comfortable and confident and won't manage a new site without them."
Speed is of the essence
Delta's machine operators have become so comfortable with the grade control systems on their compactors and big dozers that there is the risk of them fine grading when all that is needed is rough grading.
"Our operators are so prideful of their work that they are turning out fine-grade results when all we need is a faster rough grade result," says Chambliss. "The machine control systems are on those machines so they don't overfill or underfill. I want them to be close, but not necessarily exact, because in the end it's all about speed."
Delta Construction's contract calls for completion of the project in 12 months. "With our crew of 15 – rather than the 20 to 25 we would have needed without the Trimble survey and machine control – we'll complete everything in six months," states Chambliss. "But on this site, it's not about the time deadline; it's about the material. The money is made or lost in the material. And here's where the systems really demonstrated their value."
Jeff Winke is a business and construction writer based in Milwaukee, Wis. He can be reached through www.jeffwinke.com.